As known, a mechanical linear guide system is made of one or more units that slide on rectilinear guides under specific load, speed and acceleration conditions depending on the application. The most widespread sliding units of such mechanical linear guide systems are usually made of recirculating ball or roll carriages, of friction systems or of roller systems.
The sliding units made of recirculating ball or roll carriages can withstand high loads and accelerations, but have the drawback of suffering from clogging phenomena of the recirculation channel in work environments particularly polluted by dirt and dust, as well as being sensitive to misalignment. The friction systems, such as, for example, the so-called sliding or guiding “gibs”, can move large loads but suffer from problems relating to wear and cannot be used in applications where, in addition to a high load, relevant speeds are also requested.
Compared to the sliding units listed above, the linear guide roller systems have the advantage of having great flexibility and versatility of use in any environment and under operating conditions. However, even such linear guide roller systems can have at least one drawback due to possible overloads weighing on the roller themselves. If subjected to excessive loads, in fact, the rollers and/or related supporting components may break, resulting in the malfunction of the entire mechanical linear guide system and potential risks to users.
In the field of linear guide roller systems, devices auxiliary to the guide system itself have therefore been made, the function of which is to relieve the rollers of a part or the totality of the applied load, so as to avoid breakage due to the overload of one or more of the respective supporting components. These auxiliary devices are not, however, an integral part of the linear guide system, but are made of external components that intervene in certain situations in which the sole rollers would not be able to withstand the load applied to them. Such auxiliary devices may be made of, for example, load balancing or compensation devices by means of hydraulic or pneumatic cylinders, or of peak load damping devices that operate by means of shock absorbers.
Document EP 0 298 021 A1 relates to a system for the translation of sliding doors. The system comprises a carriage that slides in a respective guide. The carriage rests on a series of rotating elements configured to best distribute the load. In particular, in document EP 0 298 021 A1 there are described four rotating elements that rotate around an axis perpendicular to the translation direction of the carriage and that set such a carriage apart from the guide, avoiding premature wear caused by friction. Document EP 0 298 021 A1 therefore relates to a linear guide system, but the aims are to increase the possible weight of the door to slide, to have greater stability of the structure during movement, and to prevent wear due to the friction of the guide. In document EP 0 298 021 A1, in fact, no reference is ever made to any system of absorption of the overload that would inevitably lead to the breakage of the linear guide system. Document U.S. Pat. No. 5,070,575 A also relates to a system for the suspension and the translation of sliding doors of considerable weight when no reference is ever made to any overload absorption system.
Document DE 92 11 775 U1 relates to a linear guide system with variable preload, in which the adjustment takes automatically place through the possibility of moving the stem of one of the rollers. This movement is possible thanks to the presence of a deformable bushing, manufactured in plastic material. The aim of document DE 92 11 775 U1 is thus to perform the adjustment of a linear translation roller system, whereas the mechanical linear guide system according to the present invention provides neither the preload, nor the adjustment, but is configured to withstand both the normal load weighing on the rollers, and a possible extraordinary load which, for a normal linear translation system, could not be opposed effectively.
Document WO 2006/094734 A1 relates to a linear guide roller system wherein the possibility of self-adjusting the rollers is provided. This avoids problems of parallelism of the guides when such guides are mounted facing one another. In document WO 2006/094734 A1, the possibility of setting self-adjusting carriages is discussed, but not the load difference that can be withstood by a mechanical linear guide system of the roller type.
Document EP 0 387 168 A1 relates to a system to support and easily move loads on a plane through the use of numerous retractable hydraulic elements. Each retractable element is usually made of a sphere or a small disc that allows to direct the motion of the element itself when resting on a plane. The plane therefore comprises numerous retractable hydraulic elements, made in the form of small pistons, the task of which is to both support different load entities, and to allow the translation of the object to be supported and bring it to the desired position. The translation and the support of high loads therefore occur by contact between a fixed part and a mobile part, precisely made of the small pistons. The system described in document EP 0 387 168 A1 is typically applied on the working plane of machine tools. Unlike the system described in document EP 0 387 168 A1, the mechanical linear guide system according to the present invention is configured to support a given and/or sudden load of exceptional extent without there being mobile parts. The failure, understood as the approach of the prismatic casing to the guide on which the forces are discharged, only occurs by elastic deformation of the components (roller stems) and not by movement of any mobile part. Having mobile parts involves the drawback of increasing the wear of the components that scrape one another. Moreover, having mobile parts necessarily leads to their design and construction outside the linear guide system, which increases the costs and potentially the overall dimensions as well.
Finally, document DE 43 34 373 A1 relates to a system for moving a workpiece or a tool on a machine tool. The aim is to replace the linear translation systems of the friction or recirculation type with a roller system, as the drawbacks consist of a greater fluidity of movement and speed, in less friction and therefore less thrust force and less wear of the parts in contact. Once the working area has been reached, in order to ensure greater stability, the system provides for the support of a carriage on the machine's structure so as to have greater rigidity during operation. Such a system is similar to that described in document EP 0 387 168 A1. On the contrary, in the mechanical linear guide system according to the present invention, there is no particular area where the system itself may come into operation, but the force that is generated in the contact between the prismatic casing and the guide can be discharged at any time, anywhere along the guide.